Time filter

Source Type

Xu J.,Air force Radar Academy | Yu J.,Tsinghua University | Peng Y.-N.,Tsinghua University | Xia X.-G.,University of Delaware
IEEE Transactions on Aerospace and Electronic Systems

Based on the coupling relationship among radial velocity, range walk, and Doppler frequency of the moving target's echoes, a novel method is proposed, i.e., Radon-Fourier transform (RFT), to realize the long-time coherent integration for radar target detection. The RFT realizes the echoes spatial-temporal decoupling via joint searching along range and velocity directions, as well as the successive coherent integration via the Doppler filter bank. Besides, four equivalent RFTs are obtained with respect to the different searching parameters. Furthermore, a generalized form of RFT, i.e., generalized Radon-Fourier transform (GRFT), is also defined for target detection with arbitrary parameterized motion. Due to the similarity between the RFT and the well-known moving target detection (MTD) method, this paper provides detailed comparisons between them on five aspects, i.e., coherent integration time, filter bank structure, blind speed response, detection performance, and computational complexity. It is shown that MTD is actually a special case of RFT and RFT is a kind of generalized Doppler filter bank processing for targets with across range unit (ARU) range walk. Finally, numerical experiments are provided to demonstrate the equivalence among four kinds of RFTs. Also, it is shown that the RFT may obtain the coherent integration gain in the different noisy background and the target's blind speed effect may be effectively suppressed. In the meantime, both the weak target detection performance and the radar coverage of high-speed targets may be significantly improved via RFT without change of the radar hardware system. © 2006 IEEE. Source

Yang M.,Chongqing University | Zhou L.,Chongqing University | Zhang D.,Air force Radar Academy | Zhang M.,Chongqing University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society

Harmonic problem of the grid-connected inverters was detected in many large-scale photovoltaic(PV) plants and the harmonic problem may occurred even if all the PV inverters do individually satisfy the standards. For these reasons, the effect of grid impedance is considered, and the equivalent circuit model of three-phase grid-connected parallel inverters with LCL filter is established based on the basic structure and operating principle of the PV plants. According to the established equivalent circuit model, the influence of grid impedance in the current control loop is analyzed. Theoretical analysis indicates that grid-connected parallel inverters in PV plants are coupled due to the grid impedance, and the coupling effect can destabilize the inverter current control loop and lead to harmonic content overweight. Moreover, this study is validated by means of simulation and experiment results. Source

Liang J.,Huizhou University | Xu B.,North China University of Water Conservancy and Electric Power | Cai Z.,Air force Radar Academy
Journal of the Optical Society of America B: Optical Physics

Internal modes and internal oscillation of necklace solitons in Bessel photonic lattices imprinted in selfdefocusing and self-focusing materials are investigated. Under the same parameters, necklace solitons in selffocusing material possess larger power than that of self-defocusing material, and the stability of solitons in defocusing material is better than in focusing material. It is shown that the internal modes have both real and imaginary parts in such cases, differing from the one-dimensional case. While white noise gives rise to jitter of the intensity of stable necklace solitons, the stable solitons perform long-distance and quasi-periodic oscillation of intensity and shape under the perturbation of internal modes, and the solitons in self-defocusing material experience larger oscillation amplitude than that in self-focusing material. © 2010 Optical Society of America. Source

Ren J.,Air force Radar Academy
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011

To further research the multifractality of sea clutter, multifractality of IPIX radar sea clutter has been analyzed by Qth-order Moment Structure Partiction Function (Q-MSPF) method in detail in this paper, through simulation analysis, two target detection methods based on analysis of the mass exponent function and the source of multifractality are proposed, and proved to be effective. © 2011 IEEE. Source

Ma N.,Air force Radar Academy
Huazhong Keji Daxue Xuebao (Ziran Kexue Ban)/Journal of Huazhong University of Science and Technology (Natural Science Edition)

The system could not give full play to its performances, because multiple network cards and multiple connections technology in iSCSI can not appropriately assign every task of the system. Thus, a dynamic load balancing algorithm using a feedback control mechanism is proposed to improve the whole performance in iSCSI system. This algorithm adopts a feedback technology, collects much resource states in the whole system, and calculates the real-time feedback's value, combines the previous feedback's value to assign every system's task in order to dynamically adjust the system's load state. The test results show that the performance is improved with this algorithm. Source

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